Heme proteins dioxygen reactivity

Myoglobin in many respects is the prototypical example of the larger family of heme containing proteins and enzymes that vary in function from the relatively simple process of reversible binding of an electron to the activation of dioxygen for substrate hydroxylation. The relationship between members of this family of proteins is not based simply on structural similarities but on similarities in chemical reactivity as well. As the structure of myoglobin is relatively simple compared to other heme proteins and as it was the first for which the three-dimensional... 

The formation of [X-peroxo complexes upon exposure to dioxygen is well known for iron(II) porphyrin complexes, but p.-peroxo complexes discussed here are only transiently observed at low temperature. Thus, the formation of a stable dinuclear peroxide from the highly sterically demanding iron(II) precursor is surprising. It is also noteworthy that the carboxylate iron(II) complex is ineffective for CO binding [64]. Since nonheme iron proteins do not react with CO either, whereas iron(II) porphyrin complexes and heme proteins exhibit a high affinity toward CO, the reactivity pattern of the model complexes... 

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